This invention is in the field of half-bridge driver circuits, and relates more particularly to integrated half-bridge driver circuits capable of operating at relatively high frequencies.
Half-bridge driver circuits are presently used to drive power transistors in such applications as power converters in electronic ballasts for high intensity discharge lamps and induction lamps. Although present electronic ballast circuits operate at relatively low frequencies, typically up to several hundred KHz, electronic ballasts currently under development for high intensity discharge lamps will be required to operate at frequencies of over 700 KHz, with electronic ballasts for induction lamps requiring operation at frequencies up to several MHz. For such applications, the use of existing half-bridge driver circuits in the power converters of the electronic ballasts is impractical, because present integrated circuit designs generate high losses and excessive heat at high frequencies, which in practice limits high-voltage high-frequency operation.
A representative prior-art integrated driver circuit is the IR2110, manufactured by International Rectifier. This high-voltage integrated circuit uses a bootstrap capacitor to power the high-side gate drive circuit, which is fabricated in a floating well within the IC. Timing information from a low-voltage control circuit is communicated to the circuitry within the floating well by a level-shifting stage that operates off the high voltage and sends pulses of current to a latch circuit in the floating well. The state of the latch circuit then determines when the high-side power transistor is turned on and off. However, the use of a level shifting stage operating off the high voltage, while effective to transmit timing information to the high-side switch, is a major source of power loss at high frequencies, and in practice limits the frequency of operation of such circuits to about 100 KHz.
Accordingly, it would be desirable to have an integrated half-bridge driver circuit in which power losses due to dissipation in the level shifting circuitry are minimized or eliminated. Additionally, it would be desirable to have an integrated half-bridge driver circuit capable of operating at frequencies substantially higher than the maximum operating frequency of presently-available integrated driver circuits.